"It involves other important matters of public trust,'' Totten said in the statement. "The District Attorney's Office and the FBI are engaged in a thorough and conscientious search for the truth and are confident that we will get to the bottom of this."

Totten said he could not reveal details of the probe. But Oxnard sources said it may have been triggered by allegations of misspending on a massive city water project partly funded by the federal government.

A $250-million project known as GREAT -- the Groundwater Recovery Enhancement and Treatment program -- has been publicly criticized for cost overruns and spending more than $20,000 in city funds on a grand-opening party.

In July, district attorney's investigators requested documents known as Form 700s, which elected officials and top administrators must fill out to disclose potential conflicts of interest. Investigators asked for reams of other documents, officials said.

In his statement, Totten said those informal requests for documents "proved ineffective," prompting the Friday raid on city offices.